The formulation of effective detergent compositions which are sufficiently robust to remove a wide variety of soils and stains from fabrics under a variety of usage conditions remains a considerable challenge to the laundry detergent industry. At least equal challenges are faced by the formulator of automatic dishwashing detergent compositions (ADD's), which are expected to efficiently cleanse and sanitize dishware, often under heavy soil loads. The problems associated with the formulation of truly effective cleaning compositions have been exacerbated by legislation which limits the use of effective phosphate builders in many regions of the world.
Most conventional cleaning compositions contain mixtures of various detersive surfactants to remove a wide variety of soils and stains from surfaces. In addition, various detersive enzymes, soil suspending agents, non-phosphorus builders, optical brighteners, and the like may be added in order to boost overall cleaning performance. Many fully-formulated cleaning compositions additionally contain bleach, which typically comprises a perborate or percarbonate compound. While quite effective at high temperatures, perborates and percarbonates lose much of their bleaching function at the low to moderate temperature ranges increasingly favored in consumer product applications. Accordingly, various bleach activators such as tetraacetylethylenediamine (TAED) and nonanoyloxy-benzenesulfonate (NOBS) have been developed to potentiate the bleaching action of perborate and percarbonate across a wide temperature range. NOBS is particularly effective on "dingy" fabrics.
Despite the usage of TAED and NOBS with bleaches in various cleaning and bleaching compositions, the search continues for still more effective activator materials, especially for those which do not form diacylperoxide byproducts. In general, perhydrolysis-selective activator materials should be safe, effective, and will preferably be designed to interact with troublesome soils and stains. Recently described new bleach activators include various cationically charged activators as well as non-charged types. The majority of activators in the literature have a conjugate acid aqueous pK.sub.a value of the leaving-group which is below 13. It is generally accepted that such bleach activators perhydrolyze at a desirable rate.
It has now been determined that certain selected bleach activators are effective in removing soils and stains from fabrics and hard surfaces. These activators are unexpectedly effective despite having a leaving-group conjugate acid aqueous pK.sub.a of greater than 13. Additionally, the activators of this invention have very advantageous high ratios of rates of perhydrolysis to hydrolysis and of perhydrolysis to diacylperoxide formation. Without being limited by theory, these unusual rate ratios lead to a number of significant benefits for the bleach activators of the invention, including increased efficiency, avoidance of wasteful byproduct formation in the wash, increased color compatibility, increased enzyme compatibility, and better stability on storage.
By the present invention, commercially attractive bleach activators are provided, for example through the use of 4,5-dihydroimidazole-based chemistry. The bleach activators herein are effective for removing soils and stains not only from fabrics, but also from dishware in automatic dishwashing compositions. The activators are designed to function well over a wide range of washing or soaking temperatures. The activators herein are safe on rubber surfaces, such as the rubber sump hoses which are often used in some European front loading washing machines. Thus, the bleach activators herein provide a substantial advance over activators known in the art, as will be seen from the disclosures hereinafter.